0 Co-occurring patterns of marijuana & other illicit drug use with alcohol & tobacco are well established. Despite this & despite evidence that alcohol & tobacco may serve as gateway drugs for illicit substance use little is known about the impacts of prevention programs across substances. Specifically, we do not know whether there are declines in drug use among young people exposed to successful alcohol abuse prevention programs or alternatively whether young people affected by such programs turn toward drugs when alcohol becomes harder to obtain & less acceptable. This study tests whether patterns of marijuana & other drug use decline among college youth exposed to a successful environmental alcohol abuse prevention program that has reduced consumption & harm. Specific aims are to: 1) Describe trends in marijuana, illicit drug use, & acquisition or uptake of marijuana use among students from 10 colleges that participated in a community wide 4 year environmental alcohol abuse prevention program; 2) Compare trends in marijuana & other illicit drug use among students at 10 intervention with 32 comparison colleges; 3) Evaluate whether colleges whose students report significant declines in drug use over time are those with significant declines in alcohol use & harms; 4) Assess whether declines in illicit drug use correspond to exposure to environmental versus individually oriented prevention strategies implemented for alcohol abuse & harms. Repeated measure panel data are drawn from the Harvard College Alcohol Study and Harvard School of Public Health A Matter of Degree program evaluation which conducts intensive behavioral surveillance studies at 10 CAS colleges participating in the national AMOD demonstration & collects observational data about their alcohol-related prevention efforts. The longitudinal multi-site design is a significant advance over single institution and/or cross-sectional studies, & promises to expand our understanding about causal processes & protective mechanisms affecting drug use among college youth to improve prevention in this setting.